An implantable pacemaker may deliver pacing pulses to a patient's heart and monitor conditions of the patient's heart. The implantable pacemaker may comprise a pulse generator and one or more electrical leads. The pulse generator may be implanted in a small pocket in the patient's chest, in some examples. The electrical leads may be coupled to the pulse generator, which may contain circuitry that generates pacing pulses and/or senses cardiac electrical activity. The electrical leads may extend from the pulse generator to a target site (e.g., an atrium and/or a ventricle) where electrodes at the distal ends of the electrical leads connect to the target site. The pulse generator may provide electrical stimulation to the target site and/or monitor cardiac electrical activity at the target site via the electrodes.
In some examples, a leadless pacemaker may be used to sense electrical activity and/or deliver therapeutic signals to the heart. The leadless pacemaker may include one or more electrodes on its outer housing to deliver therapeutic electrical signals and/or sense intrinsic depolarizations of the heart. The leadless pacemaker may be positioned within or outside of the heart and, in some examples, may be anchored to a wall of the heart via a fixation mechanism.